[buddy] get rid of many recursive algorithms
This patch addresses the BuDDy part of #396, reported by Florian Renkin and Reed Oei. * src/kernel.c, src/kernel.h: Declare a bddrecstack and associated macros. Resize it when new variable are declared. * src/cache.h: Add a BddCache_index macro. * src/bddop.c (not_rec, apply_rec, quant_rec, appquant_rec, support_rec, ite_rec, compose_rec, restrict_rec, satone_rec, satoneset_rec): Rewrite using this stack to get rid of the recursion.